echoplex playback amplitude problem

[donegone]

This poor little ep-2 has had problems and each one I fix uncovers another. The first problem with the unit is that we had volume cutting in an out and unwanted distortion. I checked the multi-section filter cap(40,40,20) and the load line was very unstable and would drop in large increments. I replaced the filter cap and the output sounded much better but there still was a problem with the output signal. So I injected a 1k sine into the input and traced the signal for consistency. The signal looked good all the way up until the playback head connection to the grid of the 6EU7. The amplitude of the waveform on the carrier wave rises and falls intermittently causing the output volume to do the same. I ohmed out the playback head. It read 360ohm when the schematic called for 420ohm. I figured it was an intermittent playback head and replaced it with a new one from Mojo musical supply. No dice. The problem still occurs. I have looked into the oscillator circuit and all of the gain stages hunting for leaking coupling caps or odd voltages but have not found a problem. I replaced both of the 6EU7 tubes. I have also tested the 6C4 on a calibrated tube tester and it reads good. The waveforms produced in the oscillator circuit are stable. I don't know if this is a record head problem or if its something in the oscillator circuit. The record head ohms out at 180ohms and the schematic says it should be 160ohm. I didn't think this deviation was a large enough to consider faulty but anymore I am not sure.

[52 Bill]

The amplitude of the waveform on the carrier wave rises and falls intermittently causing the output volume to do the same.

Is the tape new? Cleaned and demagnetized the heads and tape path?

What happens with to the signal going to the record head? Try to find out if the rise and fall is being recorded on the tape or is the problem after the tape?

[donegone]

Sorry for the delay,
The signal is good all the way up until the recovery section of the playback head. I can trace the signal all the way up until R25 (47k) and then the waveform is put on a carrier produced by the local oscillator (6c4). I can see my signal on the carrier and it is consistent with no signs of rise and fall like I get right after this stage on the playback head and into V1a. My guess is that my record/erase head is bad but I didnt know if anything else could cause this. I already replaced the playback head to no avail. The oscillator seems to be fine but I have not replaced the 6C4 since my carrier looks good.